Drop down menus dont show anything

The other day I booted photoshop and all the brushes were completely gone. The brush menu was empty, and i could not get my old brushes back. Then today I tried making a new file so that I could do some homework and the unit of measurement menu showed just a scrollbar. Why is it just a scrollbar? I have reinstalled several times with and without keeping preferences and nothing worked. I really just need to work I have been using photoshop for years and I cant figure out why stuff is breaking.